"Yes I am proud to be called the father of the pill," he now says in his soothing mittel-European drawl apparently unaltered by the 60 years he has lived in America since leaving Nazi occupied Austria. "But identifying scientists is really only a surrogate for identifying the inventions or discoveries. Maybe it is true that Shakespeare's plays would never been written if it wasn't for Shakespeare. But I'm certain that if we didn't do our work then someone else would have come along shortly afterwards and done it."

This month has seen the 40th anniversary of the commercial availability of the pill. The long-standing debate as to its social, sexual, cultural and economic impact has been re-energised and broadened to take in the ethical issues arising from medical advances in fertility.

While it comes as no surprise that Djerassi, despite his apparent modesty, should energetically join in the debate on questions such as the male pill, abortion and the improved techniques for artificial insemination, the medium in which he chooses to do it is unusual. Although he does appear on the international lecture circuit and takes an innovative postgraduate class on ethics at Stanford University in California, for the past decade or so his primary activity has been as a novelist, memoirist and playwright. It is through fiction that he has chosen to take on the thorny moral and practical issues thrown up by his research half a century ago.

Djerassi has never been a typical scientist. He made his reputation as a chemist, but he has also been an astute businessman. He is a serious collector of art and owns one of the most significant private collections of Paul Klee's works in the world. As an admirer of the writings of Aldous Huxley, in the mid 1950s he personally tested out Huxley's claim that mescaline should be the opium of the intellegentsia when he and two students undertook a mescaline trip during a picnic at his house. He funded a spectacularly failed feature film in the mid-60s and has, for the past 20 years, been a benefactor to more than 1,000 writers, painters, choreographers and sculptors at an extremely successful artist's colony he founded on his California ranch.

"He's a scientist, artist, philosopher and mensch all in one," says Stephen Jay Gould who claims that Djerassi's book, The Pill, Pygmy Chimps, and Degas' Horse, "is the very best of scientific autobiography". Iris Murdoch said his 1989 debut novel, Cantor's Dilemma, was "a brilliant tale of the morals and politics of contemporary science. Exciting, moving and brilliantly written". David Lodge praises not only the content of his fictional output, but also his achievement in writing it all. "It is amazing that a man of his age who has had such a distinguished scientific career has turned to literature and is so determined to succeed."

Djerassi's chosen genre is "science-in-fiction", which is very different from science fiction because of its scrupulous scientific accuracy. In Cantor's Dilemma, which has sold more than 100,000 copies in the decade since publication, he explores the complex layers of trust between scientific colleagues. His next novel, The Bourbaki Gambit, takes on the cult of youth and the craving for name recognition in science when four distinguished old professors shake things up by pooling their work and publishing under a false name. His 1998 book, NO, illuminated the workings of the commercial bio-tech industry in relation to a pre-Viagra impotence cure. "In the novel I use the example of Muse, which was a real invention before Viagra," he explains. "But I changed the name to Musa, which is the botanical name for the banana. I still think that would have been a better trade name," he laughs.

While undoubtedly revelling in this "intellectual polygamy", Djerassi also claims it is just a practical response to the challenges he has set himself. "The more different ways we have of teaching certain difficult things the better off we are. I think that we as scientists should educate the public about the scientific and technological advances so that society can decide how best to use them. This is my missionary obsession."

He says that the idea that scientists should make moral or ethical decisions about these issues is fundamentally wrong. "Just because you have won a Nobel Prize doesn't mean you're qualified to make these important judgments. Ethics is a social construct and is something that society should establish. But in order to make educated decisions about this you must be aware of it."

Djerassi has said that the most fundamental affect the development of the pill had on him was to gradually shift his interest from the "hard" science undertaken in the lab to the "soft" science of thinking about the social conse quences arising from scientific and technological developments.

"It is already possible to choose the sex of unborn children," he explains. "The sperm of recently deceased men can be used to fertilise an egg. A woman could preserve millions of eggs when she is in her early 20s for use when she is post-menopausal in her late 40s. There is so much going on and the most important three-letter word in this century will not be "sex" but "but". For all of the wonderful opportunities these advances will throw up there will always be a but. These are things that interest me and this is what I want to start a debate about. But they are all grey questions and I don't say things are right or wrong."

David Lodge agrees that Djerassi's fiction doesn't have a specific didactic aim. "But he does have an informational or a pedagogic aim," says Lodge. "He sees fiction as a means of communicating information about science and its moral and ethical implications. There is an explicit programme to bridge the two cultures."

Lodge says that this tradition in literature can be traced back to Plato's dialogues, in which the interaction of characters is used to explore philosophical or political problems. "There is a long and honourable tradition of using fiction to explore ideas but I think that Carl would hope that his novels were rather more mainstream than that. He does aim to interest you in the plight of his characters; their weaknesses and desires and ambitions."

Djerassi himself acknowledges that such concern with literary history and technique is an unlikely turn of events. If there was a plan for his life it was that he should become a Viennese doctor like his parents. He says now that without Hitler's intervention that was what he would have become, living a bourgeois life and probably even voting for Kurt Waldheim as president.

He was born in Vienna in 1923. His mother was an Ashkenazi Jew and his father Sephardic, but he says that their home life was virtually non-religious and medicine was everything. His mother was a physician who became a dentist and his father, a Bulgarian, was a doctor who specialised in treating venereal disease in the days before penicillin. Djerassi's Barmitzvah had to be postponed when a new, and lucrative, syphilis patient presented himself at his father's clinic.

Although he remembers his early years as prosperous and enjoyable - he attended the same school as Sigmund Freud - in fact, things weren't quite as they seemed. Djerassi's parents had actually divorced when Carl was six but he didn't know this had happened until his early teens.

The first few years of his life were spent in Bulgaria so when he returned to Vienna to go to school he didn't really think it odd that he only saw his father when he came to Vienna or when the young Carl visited him during the summer. "I suppose I was simply too young and generally too happy to wonder that my parents didn't live together". The truth eventually emerged when his father was forced to introduce a girlfriend to his son.

In a strange echo of this a quarter of a century later, Djerassi himself was evasive to his children about his own first marriage, to a woman whom he had divorced before he married their mother. He had left details blank in a Who's Who entry and been vague about dates but when he eventually told his teenage daughter the truth he was relieved that she was more fascinated than traumatised by the revelation.

When the anschluss took place in April 1938 it was his father's Bulgarian nationality that saved Djerassi's life. His father returned to Vienna from Bulgaria, re-married his mother and, by July, had taken her and the 14-year-old Carl out of the country. As soon as they were safe the marriage was again annulled. Djerassi's mother went to England to arrange passage to America, while the young Carl stayed in Bulgaria where he learned English.

He didn't return to Austria until the late 1980s. "I have felt very ambivalently towards Austria for many years," he says. "They seemed to refuse to come to terms with their past in the way that Germany did."

Although he had received many awards and honorary degrees from around the world, it wasn't until a few years ago that he received a call from the Austrian consulate enquiring whether he would accept an award for culture and science. He says he gave it a lot of thought before agreeing. "When I finally did return I took the opportunity to walk around the city alone and I realised how beautiful it was, and still is, and what an extraordinary cultural mixture it represented. But it was a very bitter-sweet experience."

The journey from Vienna he began in 1938 ended in New York a year later. While his father stayed in Bulgaria, Carl and his mother arrived in America virtually penniless. "But despite everything I knew that getting an education was vital. I knew that would be my union card." He therefore took the remarkable step of writing to first lady, Eleanor Roosevelt, to explain his situation. His letter was passed on to the Institute of International Education and after a short spell in a high school in Newark he was offered a scholarship to a Presbyterian college in Missouri. By 1941, when he was only 17 and due to, "some administrative subterfuge" because he hadn't officially graduated from high school, he completed his chemistry degree in a single year at Kenyon College in Ohio before going on to do Post-graduate work at the University of Wisconsin.

Gilbert Stork, a fellow organic chemist, was a contemporary at Wisconsin and recalls Djerassi's extraordinary determination. "He had and still has the incredible ability to keep his eye on the goal," says Stork. "I remember him having this skiing accident. He had to make the very difficult decision whether to have an operation to remove his knee. This was at a time when replacement parts were not very good but he didn't hesitate for a moment. And not only does he still walk faster than most people, he even got a ski instructor to give him a technique for what amounted to skiing on one leg. He was determined that he wasn't going to be stopped skiing by the minor matter of losing a knee."

Djerassi has given considerable thought to the roots of his overwhelming determination. He describes himself a workaholic but adds that, "I'm not proud of that. I have always had the feeling that there is not enough time to get everything done".

He says that up until 1985, when he was 62, death was very much a theoretical concept. "I really considered myself immortal in the same way that most young people consider themselves immortal." He was then diagnosed with cancer of the colon. In fact, Djerassi's health has been reasonably good since then but the episode marked a sea-change in the way he lived his life.

"I took a long time to value human interaction and spontaneity. If a student said they wanted to speak to me I wouldn't say 'sit down'. I would say 'how long do you want to talk for?' and arrange a meeting in a few days. That is insulting. It took me 50 years to realise I wouldn't like to be on the receiving end of this treatment and now if I do it at least I apologise for doing it."

He says that if there is a hormone that characterises the scientific life it is testosterone. He talks about the machismo of working long hours and craving recognition from your peers. In fact he was rare among his scientific colleagues in that he had some interests outside the lab and did do things such as go to the theatre occasionally. "But the idea that scientists undertake science purely for science's sake is not quite right," he says. "We are curious but it is not just curiosity. There is also the desire for rewards. It was the same for me as well. I have lots of degrees and awards but the fact that I did not have an award from Austria for science is something that, if I didn't exactly mope around thinking about it all the time, it was something I was aware of."

This remarkable sense of drive propelled Djerassi through the early years of his career. After four years as a research chemist he joined the Swiss pharmaceutical company, CIBA, which was based in New Jersey. It was one of the original powerhouses in steroids chemistry and medicine. In 1949 he was made an associate director at Syntex in Mexico City. He says it was a bold move to go south of the Rio Grande but he felt it was right as both he and Syntex had the same goal - to establish a scientific reputation. This was initially achieved in the highly competitive field of cortisone research, which had significant impact on the treatment of arthritis. The original research into what became the pill was not initially concerned with contraception but with certain types of menstrual disorders and cancer. Other people had thought of the idea of using progesterone as a contraceptive but it would have required daily injections.

Djerassi's triumph was to develop a synthetic contraceptive that could be taken by mouth. While still working at Syntex as president of research, in 1968 he founded his own firm, Zoecon. It developed novel approaches to insect control, the gist of which is summed up in a chapter in his autobiography called How Do You Get a Cockroach to Take the Pill.

As the 60s ended so Djerassi became an increasingly public figure. He was open in his opposition to the government policy in Vietnam and made it onto the White House enemies list - as disclosed during Watergate - because of his involvement in Senator George McGovern's 1972 presidential campaign, which included serving as a delegate at Democratic convention in Miami. It was therefore an uneasy occasion for both sides when, in 1973, Djerassi was presented with the National Medal of Science by a somewhat distracted President Nixon, on the very day that Spiro Agnew, the vice president, resigned.

Gilbert Stork says that Djerassi was ready and waiting for fame when it arrived. "To a considerable extent he expected to be famous. If anything, I suspect he thought it was slower in coming than he could have reasonably expected."

Along with the fame he also acquired a considerable fortune: not from his right to the patent for the pill, for which he was given only $1 by Syntex - "that was the usual deal and I was and am entirely happy with it" - but from his ownership of stock in Syntex, which became a huge Wall Street success story, and then Zoecon. An original Syntex share cost $2. By 1993 they were valued at $8,000. He bought a large ranch near San Francisco which was called Smip - Syntex Made It Possible - and his collection of art swelled with works by the likes of Giacometti, Picasso, Henry Moore and Degas. "I liked to collect painters who were also sculptors. I was always interested in people who don't just work in one area."

But while he was increasingly professionally successful, his domestic life, already troubled, was about to be shattered. He had met his first wife when they were both at college at Kenyon and married her when he was a 19-year-old virgin. The marriage had ended after six years in 1949 when Djerassi moved to Mexico and asked for a divorce to marry Norma Lundholm, who was pregnant with Pamela, his first child. Ironically for the father of the pill, the pregnancy resulted from a broken condom.

After his son, Dale, was born in 1953 he had a vasectomy. His mother's extreme possessiveness and repeated threats of suicide had been a contributory factor in the failure of his first marriage. When her behaviour threatened his new relationship he broke off contact with her, although he continued to support her financially. She returned to New York and resumed medical practice in a hospital. He didn't see her again until many years later, when she was suffering from advanced Alzheimer's disease and did not recognise him. His relationship with his father, who came to live in America in 1949, was much better. From then until his death aged 96, they occupied neighbouring seats at the San Francisco opera.

Carl Djerassi's marriage to Norma ended in 1976 and he is now married to the Stanford literature professor and biographer, Diane Middlebrook. Dale Djerassi is a film-maker who produced the film '68 with his then wife Isabel Maxwell, daughter of Robert. Pamela Djerassi was an artist who lived on the Californian ranch with her husband. She committed suicide in 1978, when she was 28.

"It was obviously the greatest tragedy of my life," Djerassi says. "I wanted to mark her life by producing something living out of her death. Not a building or a statue." His response was to turn Smip - now named Sic Manebimus in Pace ("Thus We'll Remain in Peace") - into an artists colony.

The area was very important to Pamela and, when hiking at the ranch with her, they used to stop at a beautiful small waterfall. He told his daughter this is where he would want his ashes scattered, never dreaming that this is where he would scatter hers.

"When I go to the ranch now I do think that this wouldn't have happened if Pamela hadn't died. Of course, that doesn't make it a good thing that she died, but at least something positive came out of it."

The writer Vikram Seth and the composer John Adams, among many others, have passed through the colony. Alan Hollinghurst, the novelist, stayed there for a month while starting to write his novel The Folding Star. "It's an extraordinary place. You travel down this terrifying route called Bear Gulch Road and you do feel you've gone into another world... Djerassi has a benign, but slightly remote presence at the ranch."

The other thing Djerassi did after his daughter's death was to sell off the bulk of his art collection. "It was very traumatic but I am now glad that I did it. I know now that physical possessions are far from being the only thing that matters. I realised I could do nothing for dead artists. But with an artist's colony I could support living artists."

He has become a significant patron to many artists and a generous benefactor of art. The large Bill Woodrow sculpture in the lobby of the new British Library, of a massive book that is also a bench, was donated by Djerassi, who has a flat in Maida Vale in London and spends every summer here.

He continues to collect work by Paul Klee, whose art was being vilified by the Nazis at about the same time as Djerassi was being forced to leave Austria. Most of the collection is now housed in a special gallery at the San Francisco Museum of Modern Art and the museum will inherit the entire collection when Djerassi dies. Heather Whitmore Jain, the curatorial associate at SFMoma, looks after the collection. "What is very interesting are the similarities between Djerassi and Klee. They are both renaissance men. Klee was obviously a very creative artist, but his art is so varied and he had this scientific and methodical side to him. For instance he systematically numbered all his work and Djerassi seems to share that combination of creativity and methodicalness."

Throughout the time Djerassi was working in the commercial sector he also maintained an academic career. He was a professor at Wayne State University in Michigan and, in 1959, took up his current position as professor of chemistry at Stanford. He says he intends to be the first working professor aged 100. "I've got a chance. My father didn't die until he was 96 and that was in an accident." He had a fall after an exercise session.

His intellectual exploration of the social ramifications of his work has influenced his teaching, both in terms of subject matter and approach. He encouraged his ethics students at Stanford to write short stories. He even persuaded the prestigious Nature magazine to publish a piece of fiction for the first time in its history when the students illustrated an ethical dilemma in a renga - linked paragraphs written by different people - story. Djerassi pulled off a similar coup when the equally prestigious Science magazine included dialogue from his play about artificial insemination, An Immaculate Misconception. Orla Smith was the editor at Science who commissioned the piece. "What attracted me about the play was that it is scientifically accurate. He was discussing real scientific issues in a very interesting way."

Djerassi says that the key issue in the 21st century will be sex in an age of mechanical reproduction. "It will change the relationship between men and women in a very fundamental way. Sex and reproduction can be separated. One will be for recreation while the other will be done under a microscope."

An Immaculate Misconception was directed on BBC World Service radio by Andy Jordan, who will direct Djerassi's second play, Oxygen, co-written with the Nobel Prize-winning chemist, Roald Hoffmann, for the radio station this year. Oxygen, which looks at the culture and behavioural characteristics of chemists through the eyes of the Nobel Prize committee, will be the first play to be staged at the prize-giving conference in Sweden next year.

For someone who has operated for so long in such contentious areas Djerassi has sustained comparatively few personal or professional attacks. He says the only trouble he gets usually comes from fundamentalists of all persuasions who attend lectures billed as being by the "father of the pill".

"They expect me to be either a male chauvinist pig or a pill pusher - or both. But that is not me. I believe in a contraceptive supermarket where all sorts of contraception is available that fits with people's own personal and cultural and religious and whatever other requirements. What I don't like is other people telling them what they can and cannot use.

"I do have an opinion about abortion. I believe in a woman's right to choose. I dislike the way the debate has been characterised as pro-life and pro-abortion. The pro-life people tend to be obsessed with life before birth but pay very little attention to it afterwards. Quite often the same people who are against abortion are also against gun control and for the death penalty. I think it is impossible to make abortion illegal, so we should all work together to make it unnecessary," he says.

"But rather than say my opinion I prefer to present the arguments to people and let them debate it. That's where my genre of 'science in fiction' or 'science in theatre' has an advantage. I can enlighten people and leave a few questions in their mind. I have a motive in telling a story. It's not just to make you smile, it is also to make you think."

Life at a glance